Urine is a widely available renewable source of nitrogen and phosphorous. The nitrogen in urine is present in the form of urea, which is rapidly hydrolyzed to ammonia and carbonic acid by the urease enzymes occurring in nature. In order to efficiently recover urea, the inhibition of urease must be done, usually by increasing the pH value above 11. This method, however, usually is based on external chemical dosing, limiting the sustainability of the process. In this work, the simultaneous recovery of urea and phosphorous from synthetic urine was aimed at by means of electrochemical pH modulation. Electrochemical cells were constructed and used for urea stabilization from synthetic urine by the in situ formation of OH- ions at the cathode. In addition, phosphorous precipitation with divalent cations (Ca2+, Mg2+) in the course of pH elevation was studied. Electrochemical cells equipped with commercial (Fumasep FKE) and developmental (PSEBS SU) cation exchange membranes (CEM) were used in this study to carry out urea stabilization and simultaneous P-recovery at an applied current density of 60 A m-2. The urea was successfully stabilized for a long time (more than 1 month at room temperature and nearly two months at 4 °C) at a pH of 11.5. In addition, >82% P-recovery could be achieved in the form of precipitate, which was identified as amorphous calcium magnesium phosphate (CMP) by using transmission electron microscopy (TEM).

ELKH PE Environmental Mineralogy Research Group University of Pannonia Egyetem u 10 H 8200 Veszprém Hungary

Institute of Macromolecular Chemistry AS CR Heyrovsky Sq 2 162 06 Prague Czech Republic

Research Group on Bioengineering Membrane Technology and Energetics University of Pannonia Egyetem u 10 H 8200 Veszprém Hungary

Research Institute of Biomolecular and Chemical Engineering Nanolab University of Pannonia Egyetem u 10 H 8200 Veszprém Hungary

TailorMem Zájezd 8 273 43 Zájezd Czech Republic

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